Water flow regulation devices of the general type described above are known, e.g., by the Swiss Pat. No. 4363731 issued 12/14/82. These known devices replace with advantage the former "flood-weirs", which exist in various shapes, which comprise especially adjustable weirs which have the great disadvantage that they become blocked during dry periods, and allow the access of too much water to the purification station after heavy rainfall. The excess water exceeds by several times the capacity of the purification station. The device described in the Swiss patent is relatively expensive and, moreover, it is adapted to only one size of canalization so that it is necessary to provide a relative larger spreader which corresponds to all kind of sizes of existing canalizations.